1. Field of the Invention
The present invention generally relates to a system and method for updating background image information of a viewing area, and more specifically, to a multi-resolution background adaptation system and method.
2. Description of the Prior Art
In conventional background adaptation schemes, adaptation of a background image occurs when no activity in an entire video frame is detected. One well known approach to background adaptation is frame averaging. In this prior art method, an average of a number of input image frames is computed and used as the background image. Background adaptation based on averaging methods provide only a crude estimate of the background and do not consider the presence of moving objects in the scene. In addition, averaging is not applicable to situations in which people or objects stay in a scene for a long period of time. Moreover, averaging techniques are computationally expensive because they involve computing an average for each pixel for a plurality of image frames.
Other prior art background adaptation methods detect a sufficiently long period of time without motion in the entire frame to determine that the object has become part of the background, and then copy it into the background image. In some situations, it is difficult to determine when a video frame definitely represents the background, that is, image information for a video frame without any objects occluding parts of the background. Using the techniques of the prior art, it cannot be accurately determined whether or not an object brought into the viewing area is to become part of the actual background image information. In highly active viewing areas or scenes, a long period of no-activity is unlikely to occur. Consequently, image information associated with the object may erroneously not be incorporated into the background image.
What is needed is a background adaptation system and method which can adapt portions of a background image independently of activity in other portions of it so as to more accurately update a background image.